A luminaire, or light fixture, may be considered a complete lighting unit that receives a replaceable bulb. A bulb, or lamp, may be designed to be easily installed and removed from a light fixture. This permits rapid exchange of bulbs from the fixture, which may be free standing or fixed. The service life of the fixture may far exceed the service life of the bulb. Accordingly, some bulbs are replaced at the end of their service life by removing the bulb from a socket formed in the fixture.
The socket may mechanically support the bulb. Depending on the bulb design, the socket may couple to the bulb mechanically in a releasable manner that does not require tools either to install or to remove the bulb from the fixture. For example, some bulbs may screw into and out of the socket. Other bulbs may mechanically couple to the bulb by orienting, rotating, and translating the bulb relative to the socket. Some light fixtures are designed for the socket to provide mechanical support and electrical signals to the bulb. In some designs, terminals on the bulb make galvanic connection to corresponding terminals of the socket when the bulb is mechanically seated or engaged in the socket.
The fixture socket must provide the mechanical and/or electrical interface according to the bulb. Bulbs are available in a variety of form factors, which vary widely according to the lighting application requirements. While a bulb can be formed in a wide variety of shapes, one shape in use is an elongated tube shape. Elongate tube shapes often have two electrical terminals located at opposing ends. This elongate tube bulb structure dictates that the luminaire have corresponding spaced apart sockets to electrically couple to the bulb's electrical terminals.